I installed VirtualBox using Sulfur and yet it doesnt comes in the "Applications > System Tools".However I found a binary "VirtualBox" in the /opt/bin directory. I cant run it as root it gives error. I can run it as any other user it says permission denied. When I change its permission it wont change. It only runs from non root account and with sudo. So every time I need to run it I dosudo /opt/bin/VirtualBox

is there any other step remaining after the installation from Sulfur. Then what the heck is this Sulfur for, if it cant do proper installation ?

I've seen issues with virtualbox related with permissions in its files. So far, the only comon thing I've seen is that people where using equo/sulfur with sudo.So, try to reinstall virtualbox with su, then equo install virtualbox-bin and see if something changes.